Replace BMW Key Battery If your BMW key isn't able to open your car or turning on the engine, it could be time to change your battery. It's a simple fix. You simply need to remove the key fob, replace the battery and gently place it back. Follow these steps https://carkeyreprogramming73333.livebloggs.com/36392557/what-is-bmw-3-series-key-fob-history-history-of-bmw-3-series-key-fob